Methods and Systems for No-Touch Scanning

ABSTRACT

Aspects of the present invention are related to systems and methods for scanning a document wherein a scan function is invoked implicitly by a user positioning a document object, or document objects, to be scanned near an active surface of the scanner. According to one aspect of the present invention, the user&#39;s intent to scan a document object may be determined by an active-sensing pipeline.

FIELD OF THE INVENTION

Embodiments of the present invention relate generally to scanningdevices and methods for scanning, and, in particular, to low-cost,easy-to-use scanners.

BACKGROUND

Typical scanning devices operate on a request-driven user-interface (UI)model, wherein a scan function is invoked explicitly by a user throughthe push of a button or other similar contact means. The request-drivenUI model may be cumbersome to a user in many situations, for example,during the scanning of bound content, for example, a book, a magazine orother bound volume. Under the request-driven UI paradigm, a user mustfirst place the bound volume on the scanning surface and then initiatethe scan, often by a button press, and in some cases, by a button presson a non co-located computer networked to the scanner. This may requirethe user to release the volume being scanned, which may in turninfluence the quality of the scanned image.

Additionally, traditional line scanners may have a shallow depth offield making it difficult to capture a non-planar object due to therequirement that the object to be scanned must be placed at a precisedistance from the scan bar.

Low-cost consumer scanners are slow and require precise manufacturing toensure precision movement of the linear scan bar, and camera-baseddocument imagers employ request-driven UIs and require bulky, expensivecopy stands.

A scanning system that overcomes the above-mentioned shortcomings andother shortcomings may be desirable.

SUMMARY

Embodiments of the present invention comprise methods and systems forscanning a document. In some embodiments of the present invention, ascan function may be invoked implicitly by a user positioning adocument, or documents, to be scanned on, or near, an active surface ofa scanning device in accordance with embodiments of the presentinvention. According to one aspect of the present invention, the user'sintent to scan a document may be determined by an active-sensingpipeline.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL DRAWINGS

FIG. 1A is a picture depicting exemplary embodiments of the presentinvention comprising a scanning device communicatively coupled to acomputing system, wherein the scanning device comprises an image-capturedevice and an active surface in a “look-up” configuration;

FIG. 1B is a picture depicting exemplary embodiments of the presentinvention comprising a scanning device communicatively coupled to acomputing system, wherein the scanning device comprises an image-capturedevice and an active surface in a “look-down” configuration;

FIG. 2 is a chart showing exemplary embodiments of the present inventioncomprising detection of a static document image as a user intent toscan;

FIG. 3 is a chart showing exemplary embodiments of the present inventioncomprising a DirectShow graph implementation;

FIG. 4 is a chart showing exemplary embodiments of the present inventioncomprising a PZT-capable image-capture device;

FIG. 5 is a chart showing exemplary embodiments of the present inventioncomprising two image-capture devices;

FIG. 6 is a chart showing exemplary embodiments of the present inventioncomprising two image-capture devices, wherein one of the image-capturedevices is a PZT-capable image-capture device;

FIG. 7 is a chart showing exemplary embodiments of the present inventioncomprising optical-flow analysis; and

FIG. 8 is a chart showing exemplary embodiments of the present inventioncomprising a document tracking motion template.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments of the present invention will be best understood byreference to the drawings, wherein like parts are designated by likenumerals throughout. The figures listed above are expressly incorporatedas part of this detailed description.

It will be readily understood that the components of the presentinvention, as generally described and illustrated in the figures herein,could be arranged and designed in a wide variety of differentconfigurations. Thus, the following more detailed description of theembodiments of the methods and systems of the present invention is notintended to limit the scope of the invention, but it is merelyrepresentative of the presently preferred embodiments of the invention.

Elements of embodiments of the present invention may be embodied inhardware, firmware and/or software. While exemplary embodiments revealedherein may only describe one of these forms, it is to be understood thatone skilled in the art would be able to effectuate these elements in anyof these forms while resting within the scope of the present invention.

Typical scanning devices operate on a request-driven user-interface (UI)model, wherein a scan function is invoked explicitly by a user throughthe push of a button or other similar contact means. The request-drivenUI model may be cumbersome to a user in many situations, for example,during the scanning of bound content, for example, a book, a magazine orother bound volume. Under the request-driven UI paradigm, a user mustfirst place the bound volume on the scanning surface and then initiatethe scan, often by a button press, and in some cases, by a button presson a non co-located computer networked to the scanner. This may requirethe user to release the volume being scanned, which may in turninfluence the quality of the scanned image.

Additionally, traditional line scanners may have a shallow depth offield making it difficult to capture a non-planar object due to therequirement that the object to be scanned must be placed at a precisedistance from the scan bar.

Low-cost consumer scanners are slow and require precise manufacturing toensure precision movement of the linear scan bar, and camera-baseddocument imagers employ request-driven UIs and require bulky, expensivecopy stands.

A scanning system that overcomes the above-mentioned shortcomings andother shortcomings may be desirable.

Some embodiments of the present invention comprise a scanner system thatmay infer user intent by active sensing and may automatically initiatescanning in response to the inferred user intent.

FIG. 1A depicts exemplary embodiments of the present inventioncomprising a scanner system 2 in a “look-up” configuration. The scannersystem 2 may comprise a computing system 4 communicatively coupled, viaa communication link 6, to a scanning device 8. Exemplary computingsystems 4 may include stand-alone computing systems, distributedcomputing systems and other computing systems. In some embodiments ofthe present invention, the computing system 4 may comprise a memorystoring instructions to be executed by the computing system 4. Exemplarycommunication links 6 may include wired, wireless and othercommunication links. The scanning device 8 may comprise an assembly thathouses an image-capture device 10, for example, a camera, and atransparent imaging surface 12, referred to as an active surface,against, or near, which a planar or non-planar object to be scanned maybe placed. The active surface 12 may be observed by the image-capturedevice 10, and when scan intent is detected, the object at, or near, theactive surface 12 may be scanned. In some “look-up” configuredembodiments of the present invention, the active surface 12 may be aportion of the top surface of the scanning device 8. In alternative“look-up” configured embodiments of the present invention (not shown),an active surface may be a portion of a surface, other than the topsurface, of a scanning device, wherein the term “look-up” may refer tothe configuration in which the image-capture device views an object tobe scanned through the active surface.

FIG. 1B depicts alternative embodiments of the present inventioncomprising a scanner system 14 in a “look-down” configuration.” Thescanner system 14 may comprise a computing system 16 communicativelycoupled, via a communication link 18, to a scanning device 20. Exemplarycomputing systems 16 may include stand-alone computing systems,distributed computing systems and other computing systems. In someembodiments of the present invention, the computing system 16 maycomprise a memory storing instructions to be executed by the computingsystem 16. Exemplary communication links 18 may include wired, wirelessand other communication links. The scanning device 20 may comprise anassembly that positions an image-capture device 22, for example, acamera, above an imaging surface 24, referred to as an active surface,on, or near, which a planar or non-planar object to be scanned may beplaced. The active surface 24 may be observed by the image-capturedevice 22, and when scan intent is detected, the object on, or near, theactive surface 24 may be scanned. In some “look-down” configuredembodiments of the present invention, the active surface 24 may be anopaque surface. In alternative “look-down” configured embodiments of thepresent invention, the active surface 24 may comprise atrans-illuminated surface, which may be useful in the acquisition offilm-based objects, for example, overhead projector films, X-ray films,slides and other film-based image sources. The term “look-down” mayrefer to the configuration in which an object to be scanned may beplaced between the image-capture device 22 and the active surface 24.

In both “look-up” configured and “look-down” configured embodiments ofthe present invention, the active surface may be associated with anactive imaging region. Objects placed against the active surface or inthe active imaging region, also considered near the active surface, maybe scanned. In some embodiments of the present invention, the activeimaging region may be associated with a region near to the focal planeof the image-capture device.

In alternative embodiments (not shown), a scanner system may comprise acomputing system, for example, an embedded processor, embedded within ascanning device. The scanning device may comprise an assembly thathouses an image-capture device and an imaging surface, referred to as anactive surface, against, or near, which an object to be scanned may beplaced. The active surface may be observed by the image-capture device,and when a scan intent is detected, the object at the active surface maybe scanned. In some embodiments of the present invention, the activesurface and the image-capture device may be configured in a “look-up”configuration. In alternative embodiments of the present invention, theactive surface and the image-capture device may be configured in a“look-down” configuration.

In some embodiments (not shown), a scanning device may comprise anilluminator that may be activated prior to scanning.

In exemplary low-cost, “look-up” configured embodiments of the presentinvention, a scanning device may comprise two chambers: a lower chamberand an upper chamber. In some embodiments, a fluorescent illuminator maybe positioned to provide illumination through a first cutout in thebottom of the lower chamber. In an alternative exemplary embodiment, thefluorescent illuminator may be replaced with one, or more, LEDs (LightEmitting Diodes) attached to the inside surfaces of the lower chamber.In some of these embodiments, the lower chamber may be wallpapered withcopy bond paper to diffuse the LED illumination. A CMOS (ComplementaryMetal-Oxide Semiconductor) USB (Universal Serial Bus)-connected webcammay be positioned above the illuminator to view up towards the top ofthe assembly. The upper chamber, with a larger cutout on the top of theupper chamber, may be positioned on top of the lower chamber to adjustthe distance between the camera and the larger cutout. The upper-chambercutout may be covered with a clear, polyester, overhead transparencysheet, held in position with cellophane tape. The distance between thecamera and the larger cutout may be adjusted to a distance suitable forin-focus capture of an object placed on, or near, thetransparency-covered upper-chamber cutout. The transparent surface, ofthe scanning device, captured by the webcam is the active surface of theexemplary scanning device.

According to some embodiments of the present invention, when a scanningdevice is powered on, it may enter and remain at a low-power state untila user's intent to initiate a scan may be inferred by the scannersystem. In some embodiments of the present invention, the inference maybe made using images obtained by the image-capture device andcommunicated to the computing system.

According to alternative embodiments of the present invention, aproximity detector, for example, a photo sensor, a motion sensor orother sensor that may detect a change in conditions proximate to thelocation of the sensor, may be located on the scanning-device assembly.In these embodiments, when the image-capture device is powered down, aproximity event detected by the proximity detector may initiate apower-up process in the image-capture device, and in some embodiments,the proximity event may infer a user's intent to initiate a scan.

When an intent to scan is detected through active sensing, the scanningsystem may turn on the illumination source to facilitate a high-qualityscan and may capture an image of the object placed against, or near, theactive surface.

In some embodiments of the present invention described in relation toFIG. 2, active sensing may comprise receiving 30 an image frame,captured from an image-capture device in a scanning device, at acomputing system. In some exemplary embodiments of the presentinvention, the image frame may be transported from the scanning deviceto the computing system via a USB connection. In alternative exemplaryembodiments, the image frame may be transported internally within thescanning device to a computing system comprising an embedded processor.In yet alternative exemplary embodiments, the image frame may betransported wirelessly between the scanning device and the computingsystem.

Motion detection may be performed 32 between the received image frameand a previously captured image frame to determine if the image capturedby the image-capture device has stabilized. In some embodiments of thepresent invention, the previously captured image frame may be stored inan internal buffer within the computing system. In alternativeembodiments, the previously captured image frame may be stored outsideof the computing system and communicated to the computing system inresponse to a computing-system request or accessed directly by thecomputing system.

In some embodiments of the present invention, motion detection 32 maycomprise a frame-based motion sensor filter that performs apixel-by-pixel comparison of the received image frame and the previouslycaptured image frame.

In some embodiments, the frame-based motion sensor filter may track thenumber of significant pixel color changes between the two frames, thereceived image frame and the previously captured image frame. A pixeldifference value, which may be denoted d, may be computed at each pixellocation, indicated by i, according to:

${{d(i)} = {{\left( {2 + \frac{\mu_{R}^{(i)}}{256}} \right) \cdot {R_{d}^{2}(i)}} + {4 \cdot {G_{d}^{2}(i)}} + {\left( {2 + \frac{\left( {255 - \mu_{R}^{(i)}} \right)}{256}} \right) \cdot {B_{d}^{2}(i)}}}},$

where μ_(R) ^((i)) denotes the mean of the red component value, at pixellocation i, for the two frames, and R_(d) ²(i), G_(d) ²(i) and B_(d) ²(i) denote the squared differences between the red, green and bluecomponents at pixel location i, for the two frames, respectively. Inalternative embodiments of the present invention, a pixel colordifference may be computed according to alternative difference measuresknown in the art.

In alternative embodiments, the frame-based motion sensor filter maytrack the number of significant pixel luminance changes between the twoframes. In some of these embodiments, the image-capture device mayacquire grayscale image data, and the luminance values may be thegrayscale values. In alternative of these embodiments, the image-capturedevice may acquire color image data, and the luminance values may bedetermined, according to methods well known in the art, from the colorimage data. A pixel difference value, which may be denoted d, may becomputed at each pixel location, indicated by i, according to:

d(i)=Y _(d) ²(i),

where Y_(d) ²(i) denotes the squared differences between luminance atpixel location i, for the two frames, respectively.

If the value of a pixel difference value d(i) meets a first criterionrelative to a first threshold value, which may be denoted T_(d), thenthe pixel at location i may be considered to have changed significantly,and a counter, which may be denoted c, may be incremented. In someembodiments of the present invention, the counter c may be incrementedwhen:

d(i)>T _(d).

In alternative embodiments of the present invention, the counter c maybe incremented when:

d(i)≧T _(d).

In some embodiments of the present invention, T_(d)=10,000.

After determining the pixel difference value for each pixel, comparingthe pixel difference value for each pixel to the threshold T_(d) andappropriately incrementing the counter c, the counter value may becompared to a second threshold value, which may be denoted T_(c), todetermine 34 if the scene associated with the captured image may bestatic. In some embodiments, if the value of the counter c meets a firstcriterion relative to T_(c), then the scene may be determined not to bestatic 35. If the value of the counter c does not meet the firstcriterion relative to the second threshold value, then the scene may bedetermined to be static 36. In some embodiments, the scene may bedetermined to be non-static 35 when:

c>T_(c)

and static 36 when

c≦T_(c).

In alternative embodiments, the scene may be determined to be non-static35 when:

c≧T_(c)

and static 36 when

c<T_(c).

In some embodiments of the present invention, T_(c)=50.

When a scene is determined to be non-static 35, then subsequentprocessing of the received image frame may be skipped, and theactive-sensing pipeline may continue to analyze captured image frames30. If a scene is determined to be static 36, then document-presenceverification 38 may be performed. Document-presence verification 38 mayverify that the scanned object comprises document qualities, forexample, high-frequency content characteristic of text, pictureelements, line drawings and other content. Scanned objects that maycomprise document qualities may include planar objects, non-planarobjects and other objects. Exemplary planar objects may include documentpages, fabric pieces, leaves and other objects that may be flattened on,or near, the active surface of the scanning system. Exemplary non-planarobjects may include, bound volumes, three-dimensional objects comprisinga label or other high-frequency content and other objects that may notreadily be flattened on, or near, the active surface of the scanningsystem.

In some embodiments of the present invention, document-presenceverification 38 may comprise a gradient filter that may respond to textedges and other high-frequency content that may be typical of documentimages. Exemplary gradient filters may comprise a Canny edge detector, aSobel operator, a Laplace edge detector, a Robert's filter, a Prewittfilter, or other filters and detectors, known in the art, responsive tohigh-frequency content.

The response of the gradient filter for the current image frame may becompared 40 to reference edge data that may correspond to the edgecontent of an image, referred to as a reference image, of theunobstructed imaging surface. In some embodiments, the edge count in thecurrent frame may be compared to the edge count in the reference imagein a block-based comparison. In some embodiments, a substantive changein the number of edge pixels in one or more blocks may indicate that adocument object has 42 likely been placed on, or near, the activesurface. In some embodiments of the present invention, a change of 25%,or more, in the block edge count may indicate a substantive change. Inalternative embodiments, a detection threshold other than 25% may beused. If all blocks have been processed without detecting a substantivechange in edge pixels relative to the reference image, then the presenceof a document object is not confirmed 41, and the active-sensingpipeline may continue to analyze captured image frames 30. Alternativedocument-verification methods known in the art may be used inalternative embodiments of the present invention.

If the presence of a document object is confirmed 42, then image datafor the current frame may be captured 44 to a document buffer. In someembodiments of the present invention, the capture 44 of the currentframe to the document buffer may comprise a transfer of the storedcurrent frame to the document buffer. In alternative embodiments, thecapture 44 of the current frame to the document buffer may comprisecapturing, via the image-capture device, a current view. In someembodiments of the present invention, the capture 44 of the current viewmay be made through the image-capture device only when theactive-sensing pipeline determines an adjustment to an image-capturedevice control may be required or when a second image-capture device maybe available.

The captured image data may be made available, from the document buffer,for subsequent processing, for example, image enhancement, imagecompression, optical character recognition (OCR) analysis, and otherimage processing. The active-sensing pipeline may continue to analyzecaptured image frames 30.

Some embodiments of the present invention described in relation to FIG.3, may comprise an active-sensing pipeline constructed using theMicrosoft DirectShow API framework. The DirectShow video processinggraph of the active-sensing pipeline 50 may comprise a capture filter 52operatively coupled to a motion-detection filter 54. Themotion-detection filter 54 may be operatively coupled to anedge-detection filter 56 which may be operatively coupled to aframe-capture filter. The results of the active-sensing pipeline may bemade available 60 for subsequent processing, for example, imageenhancement, image compression, OCR analysis, and other imageprocessing, and/or may trigger user feedback, for example, audiofeedback and visual feedback.

In some exemplary embodiments of the present invention, feedback to theuser may be provided by an audio beep. In alternative embodiments,feedback to the user may be provided by a light-emitting diode (LED)flash. Alternative embodiments of the present invention may comprise asmall display for providing visual feedback, for example, a thumbnail ofthe scanned content and other visual indicators. The display may also beused to verify scan and scanner routing information.

In some embodiments of the present invention, routing information, forexample, an email address or other routing indicator, for a network scanmay be extracted, by OCR or handwriting recognition, from a page onwhich a user has written, typed, or otherwise indicated the routinginformation, and scanned using the scanning device. In some embodiments,once routing information is extracted, all additional scans may berouted to the user-provided address until the user terminates theprocess through a predetermined cue, for example, placing a blank pageon the active surface.

Some embodiments of the present invention may comprise an image-capturedevice with pan, tilt and zoom (PTZ) adjustment capabilities. In someembodiments, a first captured image may be content analyzed and based onthe content analysis, the image-capture device may be panned to optimizesensor alignment with respect to the object, or objects, in the image.The image-capture device may be tilted to center the content in thefield of view, and the image-capture device optics may be zoomed tonearly fill the sensor frame with the content.

Some embodiments of the present invention comprising a PTZ-capableimage-capture device may be described in relation to FIG. 4. In theseembodiments, active sensing may comprise receiving 70 an image frame,captured from a PTZ-capable image-capture device in a scanning device,at a computing system. In some exemplary embodiments of the presentinvention, the image frame may be transported from the scanning deviceto the computing system via a USB connection. In alternative exemplaryembodiments, the image frame may be transported internally within thescanning device to a computing system comprising an embedded processor.In yet alternative exemplary embodiments, the image frame may betransported wirelessly between the scanning device and the computingsystem.

Motion detection may be performed 72 between the received image frameand a previously captured image frame to determine if the image capturedby the PTZ-capable image-capture device has stabilized. In someembodiments of the present invention, the previously captured imageframe may be stored in an internal buffer within the computing system.In alternative embodiments, the previously captured image frame may bestored outside of the computing system and communicated to the computingsystem in response to a computing-system request or accessed directly bythe computing system.

In some embodiments of the present invention, motion detection 72 maycomprise a frame-based motion sensor filter that performs apixel-by-pixel comparison of the received image frame and the previouslycaptured image frame.

In some embodiments, the frame-based motion sensor filter may track thenumber of significant pixel color changes between the two frames, thereceived image frame and the previously captured image frame. A pixeldifference value, which may be denoted d, may be computed at each pixellocation, indicated by i, according to:

${{d(i)} = {{\left( {2 + \frac{\mu_{R}^{(i)}}{256}} \right) \cdot {R_{d}^{2}(i)}} + {4 \cdot {G_{d}^{2}(i)}} + {\left( {2 + \frac{\left( {255 - \mu_{R}^{(i)}} \right)}{256}} \right) \cdot {B_{d}^{2}(i)}}}},$

where μ_(R) ^((i)) denotes the mean of the red component value, at pixellocation i, for the two frames, and R_(d) ²(i), G_(d) ²(i) and B_(d)²(i) denote the squared differences between the red, green and bluecomponents at pixel location i, for the two frames, respectively. Inalternative embodiments of the present invention, a pixel colordifference may be computed according to alternative difference measuresknown in the art.

In alternative embodiments, the frame-based motion sensor filter maytrack the number of significant pixel luminance changes between the twoframes. In some of these embodiments, the image-capture device mayacquire grayscale image data, and the luminance values may be thegrayscale values. In alternative of these embodiments, the image-capturedevice may acquire color image data, and the luminance values may bedetermined, according to methods well known in the art, from the colorimage data. A pixel difference value, which may be denoted d, may becomputed at each pixel location, indicated by i, according to:

d(i)=Y _(d) ²(i),

where Y_(d) ²(i) denotes the squared differences between luminance atpixel location i, for the two frames, respectively.

If the value of a pixel difference value d(i) meets a first criterionrelative to a first threshold value, which may be denoted T_(d), thenthe pixel at location i may be considered to have changed significantly,and a counter, which may be denoted c, may be incremented. In someembodiments of the present invention, the counter c may be incrementedwhen:

d(i)>T _(d).

In alternative embodiments of the present invention, the counter c maybe incremented when:

d(i)≧T _(d).

In some embodiments of the present invention, T_(d)=10,000.

After determining the pixel difference value for each pixel, comparingthe pixel difference value for each pixel to the threshold T_(d) andappropriately incrementing the counter c, the counter value may becompared to a second threshold value, which may be denoted T_(c), todetermine 74 if the scene associated with the captured image may bestatic. In some embodiments, if the value of the counter c meets a firstcriterion relative to T_(c), then the scene may be determined not to bestatic 75. If the value of the counter c does not meet the firstcriterion relative to the second threshold value, then the scene may bedetermined to be static 76. In some embodiments, the scene may bedetermined to be non-static 75 when:

c>T_(c)

and static 76 when

c≦T_(c).

In alternative embodiments, the scene may be determined to be non-static75 when:

c≧T_(c)

and static 76 when

c<T_(c).

In some embodiments of the present invention, T_(c)=50.

When a scene is determined to be non-static 75, then subsequentprocessing of the received image frame may be skipped, and theactive-sensing pipeline may continue to analyze captured image frames70. If a scene is determined to be static 76, then document-presenceverification 78 may be performed. Document-presence verification 78 mayverify that the scanned object comprises document qualities, forexample, high-frequency content characteristic of text, pictureelements, line drawings and other content. Scanned objects that maycomprise document qualities may include planar objects, non-planarobjects and other objects. Exemplary planar objects may include documentpages, fabric pieces, leaves and other objects that may be flattened on,or near, the active surface of the scanning system. Exemplary non-planarobjects may include, bound volumes, three-dimensional objects comprisinga label or other high-frequency content and other objects that may notreadily be flattened on, or near, the active surface of the scanningsystem.

In some embodiments of the present invention, document-presenceverification 78 may comprise a gradient filter that may respond to textedges and other high-frequency content that may be typical of documentimages. Exemplary gradient filters may comprise a Canny edge detector, aSobel operator, a Laplace edge detector, a Robert's filter, a Prewittfilter, or other filters and detectors, known in the art, responsive tohigh-frequency content.

The response of the gradient filter for the current image frame may becompared 80 to reference edge data that may correspond to the edgecontent of an image, referred to as a reference image, of theunobstructed imaging surface. In some embodiments, the edge count in thecurrent frame may be compared to the edge count in the reference imagein a block-based comparison. In some embodiments, a substantive changein the number of edge pixels in one or more blocks may indicate that adocument object has 82 likely been placed on, or near, the activesurface. In some embodiments of the present invention, a change of 25%,or more, in the block edge count may indicate a substantive change. Inalternative embodiments, a detection threshold other than 25% may beused. If all blocks have been processed without detecting a substantivechange in edge pixels relative to the reference image, then the presenceof a document object is not confirmed 81, and the active-sensingpipeline may continue to analyze captured image frames 70. Alternativedocument-verification methods known in the art may be used inalternative embodiments of the present invention.

If the presence of a document object is confirmed 82, then the contentof the current frame may be analyzed 84, and the pan, zoom and tiltadjustments on the PZT-capable image-capture device may be adjusted 86to optimize sensor alignment with respect to the object, or objects, inthe image, to center the content in the field of view and to nearly fillthe sensor frame with the content. Then image data for the current framemay be actively captured 88 to a document buffer via the image-capturedevice. The captured image data may be made available, from the documentbuffer, for subsequent processing, for example, image enhancement, imagecompression, optical character recognition (OCR) analysis, and otherimage processing. The active-sensing pipeline may continue to analyzecaptured image frames 80.

Some embodiments of the present invention may comprise a firstimage-capture device and a second image-capture device. At least onecharacteristic of the first image-capture device and the secondimage-capture device may be different. In one exemplary embodiment, thefirst image-capture device may capture images at a lower spatialresolution than the second image-capture device. In another exemplaryembodiment, the first image-capture device may capture images at ahigher frame rate than the second image-capture device. In anotherexemplary embodiment, the first image-capture device may capture imagesat both a lower spatial resolution and a higher frame rate than thesecond image-capture device.

Embodiments of the present invention comprising two image-capturedevices may be understood in relation to FIG. 5. In these embodiments,active sensing may comprise receiving 100 an image frame, captured froma first image-capture device in a scanning device, at a computingsystem. In some exemplary embodiments of the present invention, theimage frame may be transported from the scanning device to the computingsystem via a USB connection. In alternative exemplary embodiments, theimage frame may be transported internally within the scanning device toa computing system comprising an embedded processor. In yet alternativeexemplary embodiments, the image frame may be transported wirelesslybetween the scanning device and the computing system.

Motion detection may be performed 102 between the received image frameand a previously captured image frame to determine if the image capturedby the first image-capture device has stabilized. In some embodiments ofthe present invention, the previously captured image frame may be storedin an internal buffer within the computing system. In alternativeembodiments, the previously captured image frame may be stored outsideof the computing system and communicated to the computing system inresponse to a computing-system request or accessed directly by thecomputing system.

In some embodiments of the present invention, motion detection 102 maycomprise a frame-based motion sensor filter that performs apixel-by-pixel comparison of the received image frame and the previouslycaptured image frame.

In some embodiments, the frame-based motion sensor filter may track thenumber of significant pixel color changes between the two frames, thereceived image frame and the previously captured image frame. A pixeldifference value, which may be denoted d, may be computed at each pixellocation, indicated by i, according to:

${{d(i)} = {{\left( {2 + \frac{\mu_{R}^{(i)}}{256}} \right) \cdot {R_{d}^{2}(i)}} + {4 \cdot {G_{d}^{2}(i)}} + {\left( {2 + \frac{\left( {255 - \mu_{R}^{(i)}} \right)}{256}} \right) \cdot {B_{d}^{2}(i)}}}},$

where μ_(R) ^((i)) denotes the mean of the red component value, at pixellocation i, for the two frames, and R_(d) ²(i), G_(d) ²(i) and B_(d)²(i) denote the squared differences between the red, green and bluecomponents at pixel location i, for the two frames, respectively. Inalternative embodiments of the present invention, a pixel colordifference may be computed according to alternative difference measuresknown in the art.

In alternative embodiments, the frame-based motion sensor filter maytrack the number of significant pixel luminance changes between the twoframes. In some of these embodiments, the image-capture device mayacquire grayscale image data, and the luminance values may be thegrayscale values. In alternative of these embodiments, the image-capturedevice may acquire color image data, and the luminance values may bedetermined, according to methods well known in the art, from the colorimage data. A pixel difference value, which may be denoted d, may becomputed at each pixel location, indicated by i, according to:

d(i)=Y _(d) ²(i),

where Y_(d) ²(i) denotes the squared differences between luminance atpixel location i, for the two frames, respectively.

If the value of a pixel difference value d(i) meets a first criterionrelative to a first threshold value, which may be denoted T_(d), thenthe pixel at location i may be considered to have changed significantly,and a counter, which may be denoted c, may be incremented. In someembodiments of the present invention, the counter c may be incrementedwhen:

d(i)>T _(d).

In alternative embodiments of the present invention, the counter c maybe incremented when:

d(i)≧T _(d).

In some embodiments of the present invention, T_(d)=10,000.

After determining the pixel difference value for each pixel, comparingthe pixel difference value for each pixel to the threshold T_(d) andappropriately incrementing the counter c, the counter value may becompared to a second threshold value, which may be denoted T_(c), todetermine 104 if the scene associated with the captured image may bestatic. In some embodiments, if the value of the counter c meets a firstcriterion relative to T_(c), then the scene may be determined not to bestatic 105. If the value of the counter c does not meet the firstcriterion relative to the second threshold value, then the scene may bedetermined to be static 106. In some embodiments, the scene may bedetermined to be non-static 105 when:

c>T_(c)

and static 106 when

c<T_(c).

In alternative embodiments, the scene may be determined to be non-static105 when:

c≧T_(c)

and static 106 when

c<T_(c).

In some embodiments of the present invention, T_(c)=50.

When a scene is determined to be non-static 105, then subsequentprocessing of the received image frame may be skipped, and theactive-sensing pipeline may continue to analyze captured image frames100. If a scene is determined to be static 106, then document-presenceverification 108 may be performed. Document-presence verification 108may verify that the scanned object comprises document qualities, forexample, high-frequency content characteristic of text, pictureelements, line drawings and other content. Scanned objects that maycomprise document qualities may include planar objects, non-planarobjects and other objects. Exemplary planar objects may include documentpages, fabric pieces, leaves and other objects that may be flattened on,or near, the active surface of the scanning system. Exemplary non-planarobjects may include, bound volumes, three-dimensional objects comprisinga label or other high-frequency content and other objects that may notreadily be flattened on, or near, the active surface of the scanningsystem.

In some embodiments of the present invention, document-presenceverification 108 may comprise a gradient filter that may respond to textedges and other high-frequency content that may be typical of documentimages. Exemplary gradient filters may comprise a Canny edge detector, aSobel operator, a Laplace edge detector, a Robert's filter, a Prewittfilter, or other filters and detectors, known in the art, responsive tohigh-frequency content.

The response of the gradient filter for the current image frame may becompared 110 to reference edge data that may correspond to the edgecontent of an image, referred to as a reference image, of theunobstructed imaging surface. In some embodiments, the edge count in thecurrent frame may be compared to the edge count in the reference imagein a block-based comparison. In some embodiments, a substantive changein the number of edge pixels in one or more blocks may indicate that adocument object has 112 likely been placed on, or near, the activesurface. In some embodiments of the present invention, a change of 25%,or more, in the block edge count may indicate a substantive change. Inalternative embodiments, a detection threshold other than 25% may beused. If all blocks have been processed without detecting a substantivechange in edge pixels relative to the reference image, then the presenceof a document object is not confirmed 111, and the active-sensingpipeline may continue to analyze captured image frames 100. Alternativedocument-verification methods known in the art may be used inalternative embodiments of the present invention.

If the presence of a document object is confirmed 112, then image datafor the current frame may be captured 144 from the second image-capturedevice to a document buffer. The second image-capture device capturedimage data may be made available, from the document buffer, forsubsequent processing, for example, image enhancement, imagecompression, optical character recognition (OCR) analysis, and otherimage processing. The active-sensing pipeline may continue to analyzecaptured image frames 100.

Some embodiments of the present invention may comprise two image-capturedevices of which, at least, the second image-capture device may be PTZcapable. Some of these embodiments may be understood in relation to FIG.6. In these embodiments, active sensing may comprise receiving 120 animage frame, captured from a first image-capture device in a scanningdevice, at a computing system. In some exemplary embodiments of thepresent invention, the image frame may be transported from the scanningdevice to the computing system via a USB connection. In alternativeexemplary embodiments, the image frame may be transported internallywithin the scanning device to a computing system comprising an embeddedprocessor. In yet alternative exemplary embodiments, the image frame maybe transported wirelessly between the scanning device and the computingsystem.

Motion detection may be performed 122 between the received image frameand a previously captured image frame to determine if the image capturedby the first image-capture device has stabilized. In some embodiments ofthe present invention, the previously captured image frame may be storedin an internal buffer within the computing system. In alternativeembodiments, the previously captured image frame may be stored outsideof the computing system and communicated to the computing system inresponse to a computing-system request or accessed directly by thecomputing system.

In some embodiments of the present invention, motion detection 132 maycomprise a frame-based motion sensor filter that performs apixel-by-pixel comparison of the received image frame and the previouslycaptured image frame.

In some embodiments, the frame-based motion sensor filter may track thenumber of significant pixel color changes between the two frames, thereceived image frame and the previously captured image frame. A pixelcolor difference, which may be denoted d, may be computed at each pixellocation, indicated by i, according to:

${{d(i)} = {{\left( {2 + \frac{\mu_{R}^{(i)}}{256}} \right) \cdot {R_{d}^{2}(i)}} + {4 \cdot {G_{d}^{2}(i)}} + {\left( {2 + \frac{\left( {255 - \mu_{R}^{(i)}} \right)}{256}} \right) \cdot {B_{d}^{2}(i)}}}},$

where μ_(R) ^((i)) denotes the mean of the red component value, at pixellocation i, for the two frames, and R_(d) ²(i), G_(d) ²(i) and B_(d)²(i) denote the squared differences between the red, green and bluecomponents at pixel location i, for the two frames, respectively. Inalternative embodiments of the present invention, a pixel colordifference may be computed according to alternative difference measuresknown in the art.

In alternative embodiments, the frame-based motion sensor filter maytrack the number of significant pixel luminance changes between the twoframes. In some of these embodiments, the image-capture device mayacquire grayscale image data, and the luminance values may be thegrayscale values. In alternative of these embodiments, the image-capturedevice may acquire color image data, and the luminance values may bedetermined, according to methods well known in the art, from the colorimage data. A pixel difference value, which may be denoted d, may becomputed at each pixel location, indicated by i, according to:

d(i)=Y _(d) ²(i),

where Y_(d) ² (i) denotes the squared differences between luminance atpixel location i, for the two frames, respectively.

If the value of a pixel difference value d(i) meets a first criterionrelative to a first threshold value, which may be denoted T_(d), thenthe pixel at location i may be considered to have changed significantly,and a counter, which may be denoted c, may be incremented. In someembodiments of the present invention, the counter c may be incrementedwhen:

d(i)>T _(d).

In alternative embodiments of the present invention, the counter c maybe incremented when:

d(i)≧T _(d).

In some embodiments of the present invention, T_(d)=10,000.

After determining the pixel difference value for each pixel, comparingthe pixel difference value for each pixel to the threshold T_(d) andappropriately incrementing the counter c, the counter value may becompared to a second threshold value, which may be denoted T_(c), todetermine 124 if the scene associated with the captured image may bestatic. In some embodiments, if the value of the counter c meets a firstcriterion relative to T_(c), then the scene may be determined not to bestatic 125. If the value of the counter c does not meet the firstcriterion relative to the second threshold value, then the scene may bedetermined to be static 126. In some embodiments, the scene may bedetermined to be non-static 125 when:

c>T_(c)

and static 126 when

c≦T_(c).

In alternative embodiments, the scene may be determined to be non-static125 when:

c≧T_(c)

and static 126 when

c<T_(c).

In some embodiments of the present invention, T_(c)=50.

When a scene is determined to be non-static 125, then subsequentprocessing of the received image frame may be skipped, and theactive-sensing pipeline may continue to analyze captured image frames120. If a scene is determined to be static 126, then document-presenceverification 128 may be performed. Document-presence verification 128may verify that the scanned object comprises document qualities, forexample, high-frequency content characteristic of text, pictureelements, line drawings and other content. Scanned objects that maycomprise document qualities may include planar objects, non-planarobjects and other objects. Exemplary planar objects may include documentpages, fabric pieces, leaves and other objects that may be flattened on,or near, the active surface of the scanning system. Exemplary non-planarobjects may include, bound volumes, three-dimensional objects comprisinga label or other high-frequency content and other objects that may notreadily be flattened on, or near, the active surface of the scanningsystem.

In some embodiments of the present invention, document-presenceverification 128 may comprise a gradient filter that may respond to textedges and other high-frequency content that may be typical of documentimages. Exemplary gradient filters may comprise a Canny edge detector, aSobel operator, a Laplace edge detector, a Robert's filter, a Prewittfilter, or other filters and detectors, known in the art, responsive tohigh-frequency content.

The response of the gradient filter for the current image frame may becompared 130 to reference edge data that may correspond to the edgecontent of an image, referred to as a reference image, of theunobstructed imaging surface. In some embodiments, the edge count in thecurrent frame may be compared to the edge count in the reference imagein a block-based comparison. In some embodiments, a substantive changein the number of edge pixels in one or more blocks may indicate that adocument object has 132 likely been placed on, or near, the activesurface. In some embodiments of the present invention, a change of 25%,or more, in the block edge count may indicate a substantive change. Inalternative embodiments, a detection threshold other than 25% may beused. If all blocks have been processed without detecting a substantivechange in edge pixels relative to the reference image, then the presenceof a document object is not confirmed 131, and the active-sensingpipeline may continue to analyze captured image frames 120. Alternativedocument-verification methods known in the art may be used inalternative embodiments of the present invention.

If the presence of a document object is confirmed 132, then the contentof the current frame may be analyzed 134, and the pan, zoom and tiltadjustments on the PZT-capable second image-capture device may beadjusted 136 to optimize sensor alignment with respect to the object, orobjects, in the image, to center the content in the field of view and tonearly fill the sensor frame with the content. Then image data for thecurrent frame may be captured 138 to a document buffer using the secondimage-capture device. The captured image data may be made available,from the document buffer, for subsequent processing, for example, imageenhancement, image compression, optical character recognition (OCR)analysis, and other image processing. The active-sensing pipeline maycontinue to analyze captured image frames 120.

In some embodiments of the present invention, optical-flow informationbetween a received image frame and a reference image may be used todetermine scan intent in an active-sensing pipeline. These embodimentsmay provide improved discrimination of scan intent over the pixel-basedmotion detection in the above-described embodiments of the presentinvention. Embodiments of the present invention comprising optical-flowanalysis may be useful in reducing the effects of slight movements, forexample, the movements which may be generated when a user is placing abound volume on or holding a bound volume near an active surface. Themotion trajectories associated with holding a bound volume may berandom. Alternatively, in situations where a user may be placingmultiple objects, for example, business cards, on the active surface toscan the multiple objects at one time, the motion trajectories may beconsistent between a current image and previous image.

Some embodiments of the present invention comprising optical-flowanalysis may be described in relation to FIG. 7. In these embodiments,active sensing may comprise receiving 150 an image frame, captured froman image-capture device in a scanning device, at a computing system. Insome exemplary embodiments of the present invention, the image frame maybe transported from the scanning device to the computing system via aUSB connection. In alternative exemplary embodiments, the image framemay be transported internally within the scanning device to a computingsystem comprising an embedded processor. In yet alternative exemplaryembodiments, the image frame may be transported wirelessly between thescanning device and the computing system.

Optical-flow analysis may be performed 152 between the received imageframe and a previously captured image frame to determine if the imagecaptured by the image-capture device has stabilized and if statictracking points corresponding to previously moving points remain in theframe. In some embodiments of the present invention, Lucas-Kanadeoptical-flow estimation may be used to estimate the optical-flow field.In alternative embodiments of the present invention, other optical-flowfield estimation techniques known in the art may be used. In someembodiments of the present invention, the previously captured imageframe may be stored in an internal buffer within the computing system.In alternative embodiments, the previously captured image frame may bestored outside of the computing system and communicated to the computingsystem in response to a computing-system request or accessed directly bythe computing system.

When a scene is determined 154 to be moving 155, then subsequentprocessing of the received image frame may be skipped, and theactive-sensing pipeline may continue to analyze captured image frames150. If a scene is determined to be substantially static 156, thendocument-presence verification 158 may be performed. Document-presenceverification 1588 may verify that the scanned object comprises documentqualities, for example, high-frequency content characteristic of text,picture elements, line drawings and other content. Scanned objects thatmay comprise document qualities may include planar objects, non-planarobjects and other objects. Exemplary planar objects may include documentpages, fabric pieces, leaves and other objects that may be flattened on,or near, the active surface of the scanning system. Exemplary non-planarobjects may include, bound volumes, three-dimensional objects comprisinga label or other high-frequency content and other objects that may notreadily be flattened on, or near, the active surface of the scanningsystem.

In some embodiments of the present invention, document-presenceverification 158 may be limited to a region-of-interest (ROI) associatedwith a plurality of feature points determined in the optical-flowanalysis. The corners of the document boundary may be detected asfeature points by the optical-flow analysis 152. A bounding box may befit to the extent of the feature points. In some embodiments of thepresent invention, a region-of-interest may be defined in relation tothe bounding box. In some embodiments, the bounding box may be expandedin each of the image directions by a fixed percentage, for example, 15%,to define a candidate document ROI. The fixed percentage expansionfactor may be determined to ensure that the document may be captured inits entirety accounting for document skew in relation to the imagesample grid.

In some embodiments of the present invention, document-presenceverification 158 may comprise a gradient filter that may respond to textedges and other high-frequency content that may be typical of documentimages. Exemplary gradient filters may comprise a Canny edge detector, aSobel operator, a Laplace edge detector, a Robert's filter, a Prewittfilter, or other filters and detectors, known in the art, responsive tohigh-frequency content.

The response of the gradient filter for the current image frame may becompared 160 to reference edge data that may correspond to the edgecontent of an image, referred to as a reference image, of theunobstructed imaging surface. In some embodiments, the edge count in thecurrent frame may be compared to the edge count in the reference imagein a block-based comparison. In some embodiments, a substantive changein the number of edge pixels in one or more blocks may indicate that adocument object has 162 likely been placed on, or near, the activesurface. In some embodiments of the present invention, a change of 25%,or more, in the block edge count may indicate a substantive change. Inalternative embodiments, a detection threshold other than 25% may beused. If all blocks have been processed without detecting a substantivechange in edge pixels relative to the reference image, then the presenceof a document object is not confirmed 161, and the active-sensingpipeline may continue to analyze captured image frames 150.

If the presence of a document object is confirmed 162, then image datafor the current frame ROI may be captured 164 to a document buffer. Thecaptured image data may be made available, from the document buffer, forsubsequent processing, for example, image enhancement, imagecompression, optical character recognition (OCR) analysis, and otherimage processing. The active-sensing pipeline may continue to analyzecaptured image frames 150.

In some embodiments of the present invention described in relation toFIG. 8, an image associated with the active surface may be segmentedinto several candidate regions to facilitate the tracking and separationof multiple documents, for example, business cards or receipts, placedon the active surface for scanning in a single scan. In theseembodiments, active sensing may comprise receiving 180 an image frame,captured from an image-capture device in a scanning device, at acomputing system. In some exemplary embodiments of the presentinvention, the image frame may be transported from the scanning deviceto the computing system via a USB connection. In alternative exemplaryembodiments, the image frame may be transported internally within thescanning device to a computing system comprising an embedded processor.In yet alternative exemplary embodiments, the image frame may betransported wirelessly between the scanning device and the computingsystem.

Static-object silhouettes may be identified 182 by analysis of scenemotion, between captured images over time. A motion template algorithm,for example, the algorithm taught by A. Bobick and J. Davis in“Real-time recognition of activity using temporal templates,” IEEEWorkshop on Applications of Computer Vision, pp. 39-42, December 1996and other motion template algorithms known in the art, may be used insome embodiments of the present invention to identify object silhouettesusing frame-by-frame differencing between the current image frame and apreviously captured image frame. In alternative embodiments, subtractionof a background image determined from the reference image may besubtracted from the received image frame to identify 182 static-objectsilhouettes.

For each static-object silhouette 186, document-presence verification188 may be performed in a region-of-interest (ROI) associated with thestatic-object silhouette. Document-presence verification 188 may verifythat the scanned object comprises document qualities, for example,high-frequency content characteristic of text, picture elements, linedrawings and other content. Scanned objects that may comprise documentqualities may include planar objects, non-planar objects and otherobjects. Exemplary planar objects may include document pages, fabricpieces, leaves and other objects that may be flattened on, or near, theactive surface of the scanning system. Exemplary non-planar objects mayinclude, bound volumes, three-dimensional objects comprising a label orother high-frequency content and other objects that may not readily beflattened on, or near, the active surface of the scanning system.

In some embodiments of the present invention, document-presenceverification 188 may comprise a gradient filter that may respond to textedges and other high-frequency content that may be typical of documentimages. Exemplary gradient filters may comprise a Canny edge detector, aSobel operator, a Laplace edge detector, a Robert's filter, a Prewittfilter, or other filters and detectors, known in the art, responsive tohigh-frequency content.

The response of the gradient filter for the current image frame may becompared 190 to reference edge data that may correspond to the edgecontent in the ROI of an image, referred to as a reference image, of theunobstructed imaging surface. In some embodiments, the edge count in thecurrent frame may be compared to the edge count in the reference imagein a block-based comparison. In some embodiments, a substantive changein the number of edge pixels in one or more blocks may indicate that adocument object has 192 likely been placed on, or near, the activesurface in the region associated with the ROI. In some embodiments ofthe present invention, a change of 25%, or more, in the block edge countmay indicate a substantive change. In alternative embodiments, adetection threshold other than 25% may be used. If all blocks have beenprocessed without detecting a substantive change in edge pixels relativeto the reference image, then the presence of a document object is notconfirmed 191, and the active-sensing pipeline may continue to analyzecaptured image frames 180. A document-verified region may be captured194 to a document image buffer, and after all static-object silhouetteshave been processed, then the active-sensing pipeline may continue toanalyzed captured image frames 180.

In some embodiments of the present invention, the document-verified ROIsmay be cached until the entire image frame is static. In some of theseembodiments, the ROIs may be composited to a single electronic documentfor routing. In alternative embodiments, the cached ROIs may be routedas a multi-page document. In yet alternative embodiments, each regionmay be routed individually as it is captured.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention in the use of such terms andexpressions of excluding equivalence of the features shown and describedor portions thereof, it being recognized that the scope of the inventionis defined and limited only by the claims which follow.

1. A computer-implemented method for capturing a document, said methodcomprising: a) receiving, at a computing system, an image frame from afirst image-capture device; b) comparing said received image frame witha previously captured image frame; c) when said comparison indicatesthat said received image frame has stabilized relative to saidpreviously captured image frame, determining if said received imageframe is associated with a document; and d) when said determiningindicates that said received image frame is associated with a document,capturing a document image associated with said image frame to adocument buffer.
 2. A method as described in claim 1, wherein saidcapturing a document image associated with said image frame to adocument buffer comprises a transfer of said received image frame tosaid document buffer.
 3. A method as described in claim 1 furthercomprising routing said captured document image to a first recipient. 4.A method as described in claim 3, wherein said first recipient isdetermined from a captured routing image, wherein said captured routingimage is captured prior to said receiving.
 5. A method as described inclaim 1, wherein said comparison comprises a motion filter.
 6. A methodas described in claim 1, wherein said comparison comprises determiningthe optical flow between said received image frame and said previouslycaptured image frame.
 7. A method as described in claim 1, wherein saiddetermining comprises: a) determining the high-frequency content of saidreceived image frame; and b) comparing said high-frequency content ofsaid received image frame with the high-frequency content of a referenceimage frame, wherein said reference image frame is associated with anunobstructed view of an active surface of a scanning device associatedwith said first image-capture device.
 8. A method as described in claim7, wherein said determining said high-frequency content of said receivedimage frame comprises gradient filtering said received image frame.
 9. Amethod as described in claim 1, wherein said capturing comprisescapturing said document image using said first image-capture device. 10.A method as described in claim 9, wherein said first image-capturedevice comprises at least one of a pan adjustment control, a tiltadjustment control and a zoom adjustment control.
 11. A method asdescribed in claim 10 further comprising: a) analyzing said receivedimage frame for content placement; and b) adjusting, prior to saidcapturing, at least one of said pan adjustment control, said tiltadjustment control and said zoom adjustment control in response to saidcontent placement.
 12. A method as described in claim 1, wherein saidcapturing comprises capturing said document image using a secondimage-capture device.
 13. A method as described in claim 12, whereinsaid second image-capture device comprises at least one of a panadjustment control, a tilt adjustment control and a zoom adjustmentcontrol.
 14. A method as described in claim 13 further comprising: a)analyzing said received image frame for content placement; and b)adjusting, prior to said capturing, at least one of said pan adjustmentcontrol, said tilt adjustment control and said zoom adjustment controlin response to said content placement.
 15. A system for scanning adocument, said system comprising: a) a first image-capture device; b) anactive surface; and c) a computing system communicatively coupled tosaid first image-capture device, wherein said computing system comprisesa memory storing instructions to be executed by said computing systemto: i) receive an image frame from said first image-capture device; ii)compare said received image frame with a previously captured imageframe; iii) when said comparison indicates that said received imageframe has stabilized relative to said previously captured image frame,determine if said received image frame is associated with a document;and iv) when said determining indicates that said received image frameis associated with a document, capture a document image associated withsaid image frame to a document buffer.
 16. A system as described inclaim 15, wherein said instructions to capture a document imageassociated with said image frame to a document buffer compriseinstructions to transfer said image frame to said document buffer.
 17. Asystem as described in claim 15, wherein said first image-capture devicecomprises at least one of a pan adjustment control, a tilt adjustmentcontrol and a zoom adjustment control.
 18. A system as described inclaim 17, wherein said memory stores additional instructions to beexecuted by said computing system to: a) analyze said received imageframe for content placement; and b) adjust, prior to said capturing, atleast one of said pan adjustment control, said tilt adjustment controland said zoom adjustment control in response to said content placement.19. A system as described in claim 15, wherein said instructions tocompare said received image frame with said previously captured imageframe comprise instructions to calculate a pixel color difference, ateach pixel location in said received image frame, between said receivedimage frame and said previously captured image frame.
 20. A system asdescribed in claim 15, wherein said instructions to determine if saidreceived image frame is associated with a document comprise instructionsto: a) calculate the high-frequency content of said received imageframe; and b) compare said high-frequency content of said received imageframe with the high-frequency content of a reference image frame,wherein said reference image frame is associated with an unobstructedview of said active surface.
 21. A system as described in claim 20,wherein said instructions to calculate the high-frequency content ofsaid received image frame comprise instructions to calculate a gradientof said received image frame.
 22. A system as described in claim 15further comprising a second image-capture device.
 23. A system asdescribed in claim 22, wherein said instructions to capture a documentimage associated with said image frame to a document buffer compriseinstructions to capture said document image using said secondimage-capture device.
 24. A system as described in claim 23, whereinsaid second image-capture device comprises at least one of a panadjustment control, a tilt adjustment control and a zoom adjustmentcontrol.
 25. A system as described in claim 24, wherein said memorystores additional instructions to be executed by said computing systemto: a) analyze said received image frame for content placement; and b)adjust, prior to said capturing, at least one of said pan adjustmentcontrol, said tilt adjustment control and said zoom adjustment controlin response to said content placement.
 26. A system as described inclaim 15, wherein said memory stores additional instructions to beexecuted by said computing device to route said captured document imageto a first recipient.
 27. A system as described in claim 26, whereinsaid memory stores additional instructions to be executed by saidcomputing device to determine, from a captured routing image, said firstrecipient.
 28. A system as described in claim 15, wherein saidinstructions to compare said received image frame with said previouslycaptured image frame comprise instructions to determine the optical flowbetween said received image frame and said previously captured imageframe.